transducer - a device which converts energy from one form to another

Mics convert sound waves into audio signal

All have a diaphragm - a thin piece of material that vibrates when struck by sound waves
mic-diaphragm.gif

Grouped into the type of conversion technology they use and the type of application they are designed for.
Conversion technology: the technical method the mic uses to convert the sound into electricity. Dynamic, condenser, ribbon, crystal.
Type of application: some are multi-purpose, some are specialized. Look for directional properties, frequency response and impedance.

Mic level: electrical current generated by a mic; measured in millivolts. Needs to be amplified. (low impedance)
Line level: standard signal strength. Don't need to amplify. (high impedance)
Ways to Amplify: some have tiny built-in amplifiers, some are fed through a small boosting amplifier (line amp), sound mixers have small amplifiers in each channel, power amplifier- a specialized amp which boosts the signal enough to be fed to loudspeakers.

Dynamic Microphones: versatile, simple, sturdy. No internal amplifier or external power source.
mic-dynamic.gif
Condenser Microphones: require external power. Stronger signal and more subtle than dynamic.
mic-condenser.gif

Directionality: describes the microphone's sensitivity to sound from various directions. Three categories.
Omnidirectional: picks up sound evenly from all directions
will allow bass frequencies to stay around longer when experimenting with the proximity effect because of bass coming back in the other side.
mic-polarpattern-omni.gif

Unidirectional: picks up sound predominantly from one direction (includes cardioid and hypercardioid microphones)
Cardioid:
mic-polarpattern-cardioid.gif
Hypercardioid:
mic-polarpattern-hypercardioid.gif

Bidirectional: picks up sound from two opposite directions
mic-polarpattern-bi.gif

Proximity Effect: how close you are to the mic affects the number of frequencies it picks up and the loudness of what it's picking up.

Impedance (Z): energy and resistance - when connecting devices, must match impedance level between device and what it's being received by